GEORGE MOTZ, THE AUTHOR of “Hamburger America,” has eaten a lot of burgers since he published the first edition of his book in 2008, crisscrossing the U.S. to find a very specific sort of burger joint. “You have to have a burger on the menu for at least 20 years,” Motz says. “A great burger and a great story, but the story is the least important part.” The fourth edition was published April 14 and among the 220 burger joints listed, four are in Washington — Seattle burger institutions Dick’s Drive-In and Red Mill Burgers plus two that are a bit more under the radar: Clark’s in Artic and Eastside Big Tom in Olympia. “Clark’s was new to the third edition,” Motz says. “Artic is a beautiful drive. There’s nothing out there the whole way and then suddenly there’s this restaurant! It’s a true destination.” That is no typo — Artic is an unincorporated community that runs along Highway 101, south of Montesano and Cosmopolis and north of Raymond.…